[mythtv-users] the lost minute

Romain Kang romain at kzsu.stanford.edu
Sat Apr 14 20:36:33 UTC 2007


My mythbox lost time (about 2.5 sec/minute) when I went to ivtv-0.10.
I reported this issue the ivtv-devel list.  I never got any kind of
acknowledgement or request for more information, but I managed to
workaround by turning off closed captioning in mythtvsetup:

General -> Global Backend Setup -> VBI format: None

Regarding NTP, the standard daemon from UDel cannot compensate if
the system is drifting by more than +/- 500 parts per million, and
2.5 secs/minute is about 42,000 ppm.  

Interesting /var/log/messages entries included:

Mar  3 21:27:45 nero kernel: warning: many lost ticks.
Mar  3 21:27:45 nero kernel: Your time source seems to be instable or some driver is hogging interupts
Mar  3 21:27:45 nero kernel: rip __do_softirq+0x53/0xd5

Mar  3 22:36:25 nero kernel: ivtv1 warning: CX2341X_ENC_SET_VBI_LINE took 411 jiffies (1000 per HZ)

I conjecture this could result from funny interaction between ivtv
and a single CPU system running with an SMP kernel.  (My mythbox
is running amd64 3000+ and the x86_64 kernels from Fedora Core are
all SMP).  However, I haven't had the opportunity to test the
hypothesis.

Romain


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